Gap-Acceptance and Empiricism in Capacity Prediction

The paper compares the results of extensive measurements of the capacity of nonpriority traffic streams at major/minor junctions and roundabouts with the predictions of models based on gap-acceptance theory. There are significant differences in the form of the relation between the capacity and the traffic flows in the priority streams. The simple gap-acceptance models are poor predictors of the capacity in the United Kingdom, for they seriously overpredict at low values of priority flow and underpredict at high values. At the lower values the gap-acceptance predictions can only be made to agree with the results of the empirical measurements by introducing a dependence of the “move-up” times on the value of the flows in the priority streams. The discrepancies at the higher values of priority flow are probably due to gap-forcing and priority reversal, both of which are commonly observed in the United Kingdom, but whose occurrence may vary from one country to another as a result of differences in driver behavior, legal sanctions, and enforcement policies. Several gap-acceptance models of roundabout capacities are compared and are found to be mutually inconsistent.

[1]  Gérard Louah.  Recent French Studies on Capacity and Waiting Times at Rural Unsignalized Intersections , 1988 .

[2]  R Ashworth,et al.  THE CAPACITY OF ROTARY INTERSECTIONS , 1973 .

[3]  Carlos F. Daganzo,et al.  Traffic Delay at Unsignalized Intersections: Clarification of Some Issues , 1977 .

[4]  R M Kimber,et al.  THE TRAFFIC CAPACITY OF MAJOR/MINOR PRIORITY JUNCTIONS , 1980 .

[5]  Mike McDonald,et al.  THE PREDICTION OF SATURATION FLOWS FOR ROAD JUNCTIONS CONTROLLED BY TRAFFIC SIGNALS , 1986 .

[6]  Rod Troutbeck,et al.  Capacity and delays at roundabouts - a literature review , 1984 .

[7]  E. A. Catchpole,et al.  A GENERAL CAPACITY FORMULA FOR AN UNCONTROLLED INTERSECTION , 1984 .

[8]  R. J. Troutbeck,et al.  Current and Future Australian Practices for the Design of Unsignalized Intersections , 1988 .

[9]  D. L. Gerlough,et al.  Traffic flow theory : a monograph , 1975 .

[10]  D Owens.  FLOW MEASUREMENTS AT A NUMBER OF UNCONTROLLED T-JUNCTIONS , 1960 .

[11]  R Ashworth,et al.  A NEW PROCEDURE FOR CAPACITY CALCULATIONS AT CONVENTIONAL ROUNDABOUTS. , 1978 .

[12]  I J Burrow.  THE EFFECT OF DARKNESS ON THE CAPACITY OF ROAD JUNCTIONS , 1986 .

[13]  Mike McDonald,et al.  THE CAPACITY OF ROUNDABOUTS , 1978 .

[14]  Rod Troutbeck.  Intersections, roundabouts and minis , 1988 .

[15]  Rod Troutbeck,et al.  DOES GAP ACCEPTANCE THEORY ADEQUATELY PREDICT THE CAPACITY OF A ROUNDABOUT , 1984 .

[16]  J. Tanner,et al.  A theoretical analysis of delays at an uncontrolled intersection , 1962 .

[17]  R. J. Troutbeck,et al.  Average Delay at an Unsignalized Intersection with Two Major Streams Each Having a Dichotomized Headway Distribution , 1986, Transp. Sci..

[18]  J. Tanner,et al.  The capacity of uncontrolled intersection. , 1967, Biometrika.